A typical stepped transmission or a continuously variable transmission (CVT) includes a hydraulic control system that is employed to provide cooling and lubrication to components within the transmission and to actuate torque transmitting devices such as drive clutches or torque converter clutches, belt pulley positions in CVT's, and Park positions. The conventional hydraulic control system typically includes a main pump that provides a pressurized fluid, such as oil, to a plurality of valves and solenoids within a valve body. The main pump is driven by the engine of the motor vehicle. The valves and solenoids are operable to direct the pressurized hydraulic fluid through a hydraulic fluid circuit to various subsystems including lubrication subsystems, cooler subsystems, torque converter clutch control subsystems, and shift actuator subsystems that include actuators that engage the torque transmitting devices, the pulleys that move the belt of the CVT, and an actuator that engages & disengages Park. The pressurized hydraulic fluid delivered to the pulleys is used to position the belt relative to input and output variators in order to obtain different gear ratios.
While previous hydraulic control systems are useful for their intended purpose, the need for new and improved hydraulic control system configurations within transmissions which exhibit improved performance, especially from the standpoints of efficiency, responsiveness and smoothness, is essentially constant. Accordingly, there is a need for an improved, cost-effective hydraulic control system for use in a hydraulically actuated transmission.